Some recent projectors use a light source apparatus that uses a phosphor as a light source. A light source apparatus includes an excitation light source that supplies excitation light and a phosphor unit that emits fluorescent light (visible light) by the excitation caused by excitation light that is supplied from the excitation light source.
In the above-described projector, fluorescent luminous flux that is emitted from the phosphor unit is irradiated upon a display element, and image light that is formed by the display element is projected upon a screen by projection lenses.
In the above-described light source apparatus, however, excitation light is always irradiated upon the same region of the phosphor unit, and damage (such as burns) to the phosphor caused by the excitation light may therefore occur if the intensity of the excitation light is high.
A projection-type display apparatus has therefore been proposed in which damage to the phosphor by excitation light can be mitigated (Patent Document 1).
The projection-type display apparatus described in Patent Document 1 includes: a light-emitting diode that supplies ultraviolet light, a color wheel that converts the ultraviolet light that is supplied from the light-emitting diode to visible light, a spatial modulator that is irradiated by the visible light from the color wheel, and projection lens that projects the modulated light from the spatial modulator onto a screen.
The color wheel includes a transparent substrate that can rotate, a phosphor layer that is formed on one surface of the transparent substrate, and a visible-light-reflecting layer that is formed on the other surface of the transparent substrate and that transmits ultraviolet light and reflects visible light.
The ultraviolet light from the light-emitting diode is irradiated onto the surface of the visible-light-reflecting layer of the color wheel while the color wheel is being rotated. The irradiated ultraviolet light reaches the phosphor layer and excites the phosphor. The fluorescent light that is emitted from the phosphor exits from the phosphor wheel as visible light.
Of the fluorescent light that is emitted from the phosphor, the fluorescent light that is directed toward the transparent substrate, after passing through the transparent substrate, is reflected toward the transparent substrate side at the visible-light-reflecting layer. The reflected light from the visible-light-reflecting layer transmits through the transparent substrate and the phosphor layer.
According to the above-described projection-type display apparatus, rotating the color wheel causes the light spot of the excitation light to move over the phosphor layer, whereby damage to the phosphor due to the excitation light can be mitigated.